Morphology and Ecology of Mallomonas galeiformis (Chrysophyceae), a Potentially Useful Paleolimnological Indicator

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Abstract
A total of 337 collections from 60 lakes in Connecticut and the Adirondack Mountain region of New York [USA] were processed by scanning electron microscopy for the presence of Mallomonas galeiformis. Populations were found in 35 of the collections and 11 of the lakes. Dome and domeless body scales of M. galeiformis are similar to, and often indistinguishable from, those of Mallomonas costata and Mallomonas trummensis. Posterior spined scales of M. galeiformis also are difficult to distinguish from those of M. costata. Apical domed scales with one prominent transverse shield rib, similar to ones found on Mallomonas intermedia, are described for M. galeiformis. Dome and bristle structure aid in separating M. galeiformis from morphologically similar taxa. M. galeiformis is a warm-water species that requires low specific conductance and slightly acidic conditions. The organism was more common in the Adirondack lakes, which were much lower in specific conductance values than were the Connecticut lakes. Because M. galeiformis is most common in slightly acidic conditions, but is noticeably absent below pH 5.8, it could be a pH indicator organism for use in reconstructing paleolimnological pH conditions, especially in regions having numerous water bodies with low specific conductance values.